The present invention relates to a rotary ball joint and especially to rotary ball joints for angularly movable driveshafts for motor vehicles. The rotary joints include outer joint members with ball tracks uniformly distributed on their inner circumferences. Inner joint members with the circumferentially distributed recesses are non rotatably connected to the outer joint member. The recesses are associated with the ball tracks via, preferably, three force-transmitting balls which establish form-fitting connection between the inner joint members and the outer joint members. The balls are guided in the recesses and the ball tracks.
Relevant art joints illustrated in DE PS 32 06 435 or DE-AS 1 185 868 are designed as plunging joints or fixed joints used in propeller shafts of motor vehicle drives. The force-transmitting balls are supported on a central member, in the form of a cone or a ball, in the inner joint part. Depending on the articulation angle the force transmitting balls are subject to, a greater or lesser sliding friction will occur.
DE 28 04 778 C3 illustrates, for the purpose of reducing sliding friction, a telescopic driveshaft with force-transmitting balls received on guiding balls which ride in circular grooves in planes perpendicular to radial axes. The guiding balls rollingly rotate in only the direction of the circular grooves. Sliding friction occurs when the force-transmitting balls roll in the outer ball tracks.
GB-PS 1 266 501 illustrates support balls for ball rolling elements in a bearing bush guided by bearing balls. The bearing bushes are resiliently held, which means that the balls cannot transmit any transverse forces.
It is the object of the present invention to provide a rotary ball joint with force-transmitting balls, which, under joint articulation and axial vibrations, are able to rotate in their tracks in the outer member and in recesses in the inner member, while causing substantially no sliding friction.
The objective is achieved by supporting the force-transmitting balls in partially spherical sockets in the inner joint member by bearing balls. With the help of this measure it is possible to provide a rotary ball joint which is characterized by lower friction losses and ensures a reduction in axial excitation which provides easy plunging even under articulation angles. The bearing balls are free moving with respect to one another and held in the ball sockets by spring rings near the upper rim.
To avoid any mechanical forcing while ensuring the largest possible ball contact, at the base of the ball socket a clearance is present between the force-transmitting balls and bearing balls. Preferably, the ball sockets are produced in a non-chip-forming way, at least at said base of the ball sockets to reduce production costs. Several cross sectional shapes are proposed for the tracks in the outer joint member. In particular, the tracks in the outer joint member may include a base ball contacting region.
From the following detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.